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对在350℃长时间时效的异种NiCrMoV钢接头进行冲击试验发现,时效处理后焊缝冲击性能下降明显。通过光学显微镜、扫描电镜、电子背散射衍射分析、化学成分和微观组织分析,结果表明:M3C碳化物沿晶界析出、溶质原子N在晶界偏聚和时效过程中残余奥氏体的热失稳分解是导致异种NiCrMoV钢接头时效后性能下降的主要原因。
Impact tests on dissimilar NiCrMoV steel joints aged at 350 ℃ for a long time showed that the impact properties of the weld after aging were obviously decreased. The results of optical microscopy, scanning electron microscopy, electron backscatter diffraction analysis, chemical composition and microstructure analysis show that the carbides of M3C are precipitated along the grain boundaries and the thermal loss of retained austenite during segregation and aging of the solute atoms N Stable decomposition is the main reason for the performance degradation of dissimilar NiCrMoV steel joints after aging.